_Credulity_ The physical origin of mental delusion has many times been investigated and explained by various philosophers, but the different forms of credulity and superstition have never yet been satisfactorily treated with reference to the physiological and pathological principles upon which they depend. From the beginning, man was and is, by nature, endowed with an eager propensity for novelty. This is particularly true of Americans. His passion for the novel, the singular and the unusual, has influenced his mind to attempt to discover the character of objects concealed in the remote recesses of infinite space, and to investigate the various invisible agencies that he has always found, and still finds, in perpetual operation around him. Curiosity has always been one of the great impelling forces of the scientific investigator. As Winwood Reade says in his masterly "Martyrdom of Man," "The Philosophic spirit of inquiry may be traced to brute curiosity, and that to the habit of examining all things in search of food." Man is by nature a credulous, and at the same time a superstitious, being, and ever prone to allow an undue influence to the imagination and passions. This is due to the original structure and specific elements of the mind. It is a natural trait of the mind to contemplate with interest whatever is presented to it as deviating from ordinary natural events, whatever is novel or strange, and whatever affects the senses, through an obscure medium so as to arouse the passions. Thus, when primeval man first felt, saw or heard such natural phenomena as volcanic eruptions, earthquakes, the aurora borealis, thunder, lightning, meteors, and eclipses, it was quite natural for him to people the hidden recesses of the earth and of space with demons, and to imagine that these strange noises and sights were manifestations of some powerful enemy. In his blind ignorance, he could ascribe no natural causes to the phenomena, and he therefore attributed them to supernatural agencies. His feeling of dependence, and of insecurity, in the face of these mighty unknown forces, inclined him to seek a protector, and for this purpose he created one or more gods. Idols of various kinds answered the purpose, until his dawning intelligence taught him the futility of this sort of worship, and then he worshipped the sun and other heavenly bodies. Then a glimpse of astronomy further enlightened him, and, realizing the absurdity of planet worship, he invented other gods of an invisible nature to which he attributed the creation of all phenomena. The propensity for the novel and marvelous always obscured his reason and judgment. To the ignorant mind, everything marvelous is super-natural; but the philosopher sees in all marvelous phenomena nothing but the results of natural causes, even if those causes are not yet fully understood. Science cannot yet fathom all of nature's mysteries, but nearly every day brings forth new light.